It is only when the historian deals with the relatively moderate dimensions of the force left behind with Mardonius in 479, which he says amounted to 300,000 men, that his evidence on this particular point becomes worthy of consideration. The numbers he gives of the Greek contingents at Platæa, derived apparently from some official information, amount altogether to over 100,000 men. It may be regarded as certain that Mardonius did not face the Greek on that occasion with an army in a less proportion than two to one to that of the enemy. If so, Herodotus’ statements must approximate to the truth. It is probable, too, that Mardonius retained with him a considerable fraction of the original land force, and this would be in general accord with an estimate of over half a million for the total numbers of the land army.[95] The preparation and collection of such a force, drawn from every race in that extensive empire, would be necessarily a work of time; and, apart from this, the Orient does not work quickly. Whatever the faults committed in the war, the excellence of the organization on the Persian side must, in certain important respects, have been remarkable; and that organization cannot, for the purposes of an expedition of such magnitude, have been a brief work. The exaggeration in Herodotus’ statement that the expedition took four years to prepare, may not, therefore, be very great. One deduction must be made. Egypt was not reduced until Darius had been dead a year, and therefore its reduction may fall _late_ in 484; and, if so, the period of preparation cannot have greatly exceeded three years. It was early in these years of preparation that labourers were sent to cut a canal through the low and narrow isthmus which connects Mount Athos with the mainland of Chalkidike. The disaster to Mardonius’ expedition in 492 had aroused within the Persian breast a dread of this formidable promontory. The plan of the expedition was, indeed, a return to that of the expedition of 492. Marathon had shown the Persians that an attack on Greece, or even on Athens, in order to be successful, must be organized on a larger scale than any expedition which could be put on board a fleet The expedition of Mardonius had been successful as far as human agency was concerned; that of Datis and Artaphernes, though launched against an infinitely less formidable object of attack, had been a serious failure. The most natural way of accounting for the contrast would be the comparison of size. While the canal at Athos was in process of construction, a bridge was being built over the Strymon river, and ropes were being prepared for the great bridges by which it was proposed to cross the Hellespont. Large depôts of provisions were also collected at various points on the intended route, at Leuké Akté in Thrace, at Tyrodiza in Perinthia, at Doriskos, at Eion, and in Macedonia. CHAPTER VI.